Interference reduction for tof systems

ABSTRACT

Embodiments disclosed herein are directed to time-of-flight (TOF) systems, and methods for use therewith, that substantially reduce interference that the TOF system may cause to at least one other system that is configured to wirelessly receive and respond to IR light signals. Some such embodiments involve emitting IR light having a low frequency (LF) power envelope that is shaped to substantially reduce frequency content within at least one frequency range known to be used by at least one other system that may be in close proximity to the TOF system. Such embodiments can also involve detecting at least a portion of the emitted RF modulated IR light that has reflected off one or more objects. A TOF system can produce depth images in dependence on results of the detecting, as well as update an application in dependence on the depth images.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/822,873, filed May 13, 2013, which is incorporated herein byreference.

BACKGROUND

Various consumer electronic devices, such as televisions, set top boxesand media players, are configured to be remotely controlled by handheldremote control devices that transmit modulated infrared (IR) remotecontrol signals. Such IR remote control signals typically have awavelength of about 940 nm and typically have a carrier frequencybetween 10 kHz and 100 kHz, and even more specifically between 30 kHzand 60 kHz. For an even more specific example, many IR remote controlsignals have a carrier frequency of about 36 kHz (this is not to beconfused with the actual frequency of the IR light itself).

A time-of-flight (TOF) camera, which can also be referred to as a TOFsystem, may be located in close proximity to (e.g., within the same roomas) one or more of the aforementioned consumer electronic devices (e.g.,a television, a set top box and/or a media player) that is/areconfigured to be remotely controlled by a handheld remote controldevice. For example, a TOF camera may be part of a gaming console thatis within the same room as a television, a set top box and/or a DVDplayer, which can also be referred to as other systems. Such a TOFcamera typically operates by illuminating a target with a modulated IRlight source and detecting IR light that reflects off the target and isincident on an image pixel detector array of the TOF camera. The IRlight source is usually modulated at a relatively high carrier frequency(e.g., about 100 MHz, which is within the radio frequency range) duringintegration and is typically switched off between frames or captures andduring readout. While the carrier frequency of the modulated IR lightsource is typically well above the carrier frequency of remote controlsignals, transitions from times during which the light source does notemit the RF modulated light to times during which the light source emitsRF modulated light, and vice versa, can produce lower frequency contentthat can interfere with the remote control signals. Explained anotherway, a low frequency (LF) power envelope associated with the modulatedIR light, produced by the TOF camera, may interfere with remote controlsignals intended to control another system (e.g., a television) withinclose proximity to the TOF camera. A vast majority of the interferenceproduced by the TOF camera will not correspond to a valid remote controlcommand, and thus, will be rejected by an IR receiver of the othersystem (e.g., the television) that is intended to be controlled byremote control signals. However, the interference produced by the TOFcamera may be significant enough to prevent a user from being able toactually remotely control the other system (e.g., the television) thatis within close proximity to the TOF camera. This can be frustrating tothe user, as they may not be able to adjust the volume, brightness,channel, and/or the like, of the other system (e.g., the television)using the remote control device. In other words, a TOF camera can rendera remote control device inoperative. Due to relatively poor opticalbandpass characteristics of IR receives of televisions, or othersystems, such interference problems may even occur where the IRwavelength used by a TOF camera differs from the IR wavelength used by aremote control device. For example, such interference problems may evenoccur where the wavelength of the IR light used by the TOF camera isabout 860 nm and the IR light used by a remote control device is about940 nm. Further, it is noted that a TOF camera may also cause similarinterference problems with other systems that receive and respond towireless IR signals, such as, but not limited to, systems that includewireless IR headphones and three-dimensional (3D) television systemsthat include active shutter 3D glasses.

SUMMARY

Certain embodiments disclosed are directed to time-of-flight (TOF)systems, and methods for use therewith, that substantially reduceinterference that the TOF system may cause to at least one other systemthat is configured to wirelessly receive and respond to IR lightsignals. Some such embodiments involve emitting IR light having a lowfrequency (LF) power envelope that is shaped to substantially reducefrequency content within at least one frequency range known to be usedby at least one other system configured to wirelessly receive andrespond to IR light signals, wherein at least a portion of IR lightbeing emitted is radio frequency (RF) modulated IR light, and thus,includes an RF component. Such embodiments can also involve detecting atleast a portion of the emitted RF modulated IR light that has reflectedoff one or more objects. A TOF system can produce depth images independence on results of the detecting, as well as update an applicationin dependence on the depth images. A LF power envelope, as the term isused herein, is the LF average power delivered over time by a signal.

A TOF system can be configured to obtain a separate depth imagecorresponding to each of a plurality of frame periods, wherein eachframe period is followed by an inter-frame period, each frame periodincludes at least two integration periods, and each integration periodis followed by a readout period. IR light can be emitted during each ofthe integration periods, to enable depth images to be produced.Additionally, to reduce how often there are transitions from timesduring which IR light is being emitted and times during which IR lightis not being emitted, and thereby reduce frequency content associatedwith the transitions, the IR light can also be emitted during thereadout periods between pairs of the integration periods within eachframe period.

In certain embodiments, in order to decrease a gain level of anautomatic gain control (AGC) circuit for use with an IR light receiverof at least one other system configured to wirelessly receive andrespond to IR light signals, and thereby make the IR light receiver ofthe at least one other system less sensitive to interference from theTOF system, IR light can be emitted during the readout periods betweenpairs of the integration periods within each frame period, as well asduring at least a portion the inter-frame periods between pairs offrames. This can be in addition to the IR light that is emitted duringthe integration periods.

IR light may be emitted by producing a drive signal including an RFcomponent and having a LF power envelope that is shaped to substantiallyreduce frequency content within at least one frequency range known to beused by at least one other system configured to wirelessly receive andrespond to IR light signals, and driving at least one light source withthe drive signal including the RF component.

In an embodiment, the LF power envelope can be shaped by ramping uppulse amplitudes of the drive signal when transitioning from a timeduring which no light source is driven to emit IR light to a time duringwhich a light source is driven by the drive signal to emit IR light, andramping down pulse amplitudes of the drive signal when transitioningfrom a time during which a light source is driven by the drive signal toemit IR light to a time during which no light source is driven to emitIR light.

In an embodiment, the LF power envelope can be shaped by ramping uppulse duty cycles of the drive signal when transitioning from a timeduring which no light source is driven to emit IR light to a time duringwhich a light source is driven by the drive signal to emit IR light, andramping down pulse duty cycles of the drive signal when transitioningfrom a time during which a light source is driven by the drive signal toemit IR light to a time during which no light source is driven to emitIR light.

In an embodiment, the LF power envelope can be shaped by ramping downtemporal gaps between pulses or pulse trains of the drive signal whentransitioning from a time during which no light source is driven to emitIR light to a time during which a light source is driven by the drivesignal to emit IR light, and ramping up temporal gaps between pulses orpulse trains of the drive signal when transitioning from a time duringwhich a light source is driven by the drive signal to emit IR light to atime during which no light source is driven to emit IR light.

In an embodiment, the LF power envelope can be shaped by ramping downhow often gaps occur between pulses or pulse trains of the drive signalwhen transitioning from a time during which no light source is driven toemit IR light to a time during which a light source is driven by thedrive signal to emit IR light, and ramping up how often gaps occurbetween pulses or pulse trains of the drive signal when transitioningfrom a time during which a light source is driven by the drive signal toemit IR light to a time during which no light source is drive to emit IRlight.

Any of the aforementioned ramping up preferably occurs over a timeperiod of at least 50 μsec, and any of the aforementioned ramping downpreferably also occurs over a time period of at least 50 μsec. Timepermitting, the ramping up and ramping down may occur over longerperiods of time.

More generally, embodiments of the present technology can be used toreduce the adverse effects that TOF systems may have on other systemsthat are configured to wirelessly receive and respond to IR lightsignals, while preserving correct TOF operation. Such embodimentspreferably do not degrade, or minimally degrade, performance of TOFsystems. Additionally, such embodiments preferably do not increase, orminimally increase, power usage by TOF system.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter. Furthermore, the claimed subject matter is not limited toimplementations that solve any or all disadvantages noted in any part ofthis disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate an example embodiment of a tracking systemwith a user playing a game.

FIG. 2A illustrates an example embodiment of a capture device that maybe used as part of the tracking system.

FIG. 2B illustrates an exemplary embodiment of a TOF camera that may bepart of the capture device of FIG. 2A.

FIG. 3 illustrates an example embodiment of a computing system that maybe used to track user behavior and update an application based on theuser behavior.

FIG. 4 illustrates another example embodiment of a computing system thatmay be used to track user behavior and update an application based onthe tracked user behavior.

FIG. 5 illustrates an exemplary depth image.

FIG. 6 depicts exemplary data in an exemplary depth image.

FIG. 7 illustrates exemplary timing and amplitude details associatedwith two exemplary frames of a signal for use with a TOF system.

FIG. 8 illustrates an exemplary LF frequency power spectrum associatedwith the signal shown in FIG. 7.

FIG. 9 illustrates how the LF power spectrum of drive and IR lightsignals can be shaped, in accordance with an embodiment, tosubstantially reduce frequency content within at least one frequencyrange known to be used by at least one other system configured towirelessly receive and respond to IR light signals.

FIG. 10 illustrates how the LF power spectrum of drive and IR lightsignals can be shaped, in accordance with another embodiment, tosubstantially reduce frequency content within at least one frequencyrange known to be used by at least one other system configured towirelessly receive and respond to IR light signals.

FIG. 11 illustrates how the LF power spectrum of drive and IR lightsignals can be shaped, in accordance with still another embodiment, tosubstantially reduce frequency content within at least one frequencyrange known to be used by at least one other system configured towirelessly receive and respond to IR light signals.

FIG. 12 illustrates an embodiment that reduces how often there aretransitions from times during which IR light signals are emitted totimes during which the IR light signals are not emitted, and vice versa,to thereby reduce certain frequency content associated with suchtransitions.

FIG. 13 illustrates an embodiment that combines the embodiments of FIGS.9 and 12.

FIG. 14 illustrates an embodiment that decreases a gain level set by anautomatic gain control (AGC) circuit associated with a receiver ofanother system in close proximity to a TOF system, and thereby, makesthe receiver of the other system less susceptible to interference fromthe TOF system.

FIG. 15 illustrates an additional technique for smoothing out LF powerenvelopes in accordance with an embodiment.

FIG. 16 is a high level flow diagram that is used to summarize methodsaccording to various embodiments of the present technology.

DETAILED DESCRIPTION

Certain embodiments of the present technology disclosed herein aredirected to TOF systems, and methods for user therewith, thatsubstantially reduce interference that a TOF system may cause to atleast one other system (e.g., a television, a set top box, a DVD player,IR headphones and/or active 3D glasses) that is configured to wirelesslyreceive and respond to IR light signals. Before providing additionaldetails of such embodiments of the present technology, exemplary detailsof systems with which embodiments of the present technology can be usedwill first be described.

FIGS. 1A and 1B illustrate an example embodiment of a tracking system100 with a user 118 playing a boxing video game. In an exampleembodiment, the tracking system 100 may be used to recognize, analyze,and/or track a human target such as the user 118 or other objects withinrange of the tracking system 100. As shown in FIG. 1A, the trackingsystem 100 includes a computing system 112 and a capture device 120. Aswill be describe in additional detail below, the capture device 120 canbe used to obtain depth images and color images (also known as RGBimages) that can be used by the computing system 112 to identify one ormore users or other objects, as well as to track motion and/or otheruser behaviors. The tracked motion and/or other user behavior can beused to update an application. Therefore, a user can manipulate gamecharacters or other aspects of the application by using movement of theuser's body and/or objects around the user, rather than (or in additionto) using controllers, remotes, keyboards, mice, or the like. Forexample, a video game system can update the position of images displayedin a video game based on the new positions of the objects or update anavatar based on motion of the user.

The computing system 112 may be a computer, a gaming system or console,or the like. According to an example embodiment, the computing system112 may include hardware components and/or software components such thatcomputing system 112 may be used to execute applications such as gamingapplications, non-gaming applications, or the like. In one embodiment,computing system 112 may include a processor such as a standardizedprocessor, a specialized processor, a microprocessor, or the like thatmay execute instructions stored on a processor readable storage devicefor performing the processes described herein.

The capture device 120 may include, for example, a camera that may beused to visually monitor one or more users, such as the user 118, suchthat gestures and/or movements performed by the one or more users may becaptured, analyzed, and tracked to perform one or more controls oractions within the application and/or animate an avatar or on-screencharacter, as will be described in more detail below.

According to one embodiment, the tracking system 100 may be connected toan audiovisual device 116 such as a television, a monitor, ahigh-definition television (HDTV), or the like that may provide game orapplication visuals and/or audio to a user such as the user 118. Forexample, the computing system 112 may include a video adapter such as agraphics card and/or an audio adapter such as a sound card that mayprovide audiovisual signals associated with the game application,non-game application, or the like. The audiovisual device 116 mayreceive the audiovisual signals from the computing system 112 and maythen output the game or application visuals and/or audio associated withthe audiovisual signals to the user 118. According to one embodiment,the audiovisual device 16 may be connected to the computing system 112via, for example, an S-Video cable, a coaxial cable, an HDMI cable, aDVI cable, a VGA cable, component video cable, or the like.

As shown in FIGS. 1A and 1B, the tracking system 100 may be used torecognize, analyze, and/or track a human target such as the user 118.For example, the user 118 may be tracked using the capture device 120such that the gestures and/or movements of user 118 may be captured toanimate an avatar or on-screen character and/or may be interpreted ascontrols that may be used to affect the application being executed bycomputing system 112. Thus, according to one embodiment, the user 118may move his or her body to control the application and/or animate theavatar or on-screen character.

In the example depicted in FIGS. 1A and 1B, the application executing onthe computing system 112 may be a boxing game that the user 118 isplaying. For example, the computing system 112 may use the audiovisualdevice 116 to provide a visual representation of a boxing opponent 138to the user 118. The computing system 112 may also use the audiovisualdevice 116 to provide a visual representation of a player avatar 140that the user 118 may control with his or her movements. For example, asshown in FIG. 1B, the user 118 may throw a punch in physical space tocause the player avatar 140 to throw a punch in game space. Thus,according to an example embodiment, the computer system 112 and thecapture device 120 recognize and analyze the punch of the user 118 inphysical space such that the punch may be interpreted as a game controlof the player avatar 140 in game space and/or the motion of the punchmay be used to animate the player avatar 140 in game space.

Other movements by the user 118 may also be interpreted as othercontrols or actions and/or used to animate the player avatar, such ascontrols to bob, weave, shuffle, block, jab, or throw a variety ofdifferent power punches. Furthermore, some movements may be interpretedas controls that may correspond to actions other than controlling theplayer avatar 140. For example, in one embodiment, the player may usemovements to end, pause, or save a game, select a level, view highscores, communicate with a friend, etc. According to another embodiment,the player may use movements to select the game or other applicationfrom a main user interface. Thus, in example embodiments, a full rangeof motion of the user 118 may be available, used, and analyzed in anysuitable manner to interact with an application.

In example embodiments, the human target such as the user 118 may havean object. In such embodiments, the user of an electronic game may beholding the object such that the motions of the player and the objectmay be used to adjust and/or control parameters of the game. Forexample, the motion of a player holding a racket may be tracked andutilized for controlling an on-screen racket in an electronic sportsgame. In another example embodiment, the motion of a player holding anobject may be tracked and utilized for controlling an on-screen weaponin an electronic combat game. Objects not held by the user can also betracked, such as objects thrown, pushed or rolled by the user (or adifferent user) as well as self-propelled objects. In addition toboxing, other games can also be implemented.

According to other example embodiments, the tracking system 100 mayfurther be used to interpret target movements as operating system and/orapplication controls that are outside the realm of games. For example,virtually any controllable aspect of an operating system and/orapplication may be controlled by movements of the target such as theuser 118.

FIG. 2A illustrates an example embodiment of the capture device 120 thatmay be used in the tracking system 100. According to an exampleembodiment, the capture device 120 may be configured to capture videowith depth information including a depth image that may include depthvalues via any suitable technique including, for example,time-of-flight, structured light, stereo image, or the like. Accordingto one embodiment, the capture device 120 may organize the depthinformation into “Z layers,” or layers that may be perpendicular to a Zaxis extending from the depth camera along its line of sight.

As shown in FIG. 2A, the capture device 120 may include an image cameracomponent 222. According to an example embodiment, the image cameracomponent 222 may be a depth camera that may capture a depth image of ascene. The depth image may include a two-dimensional (2-D) pixel area ofthe captured scene where each pixel in the 2-D pixel area may representa depth value such as a distance in, for example, centimeters,millimeters, or the like of an object in the captured scene from thecamera.

As shown in FIG. 2A, according to an example embodiment, the imagecamera component 222 may include an infra-red (IR) light component 224,a three-dimensional (3-D) camera 226, and an RGB camera 228 that may beused to capture the depth image of a scene. For example, intime-of-flight (TOF) analysis, the IR light component 224 of the capturedevice 120 may emit an infrared light onto the scene and may then usesensors (not specifically shown in FIG. 2A) to detect the backscatteredlight from the surface of one or more targets and objects in the sceneusing, for example, the 3-D camera 226 and/or the RGB camera 228. Insome embodiments, pulsed IR light may be used such that the time betweenan outgoing light pulse and a corresponding incoming light pulse may bemeasured and used to determine a physical distance from the capturedevice 120 to a particular location on the targets or objects in thescene. Additionally or alternatively, the phase of the outgoing lightwave may be compared to the phase of the incoming light wave todetermine a phase shift. The phase shift may then be used to determine aphysical distance from the capture device to a particular location onthe targets or objects. Additional details of an exemplary TOF type of3-D camera 226 are described below with reference to FIG. 2B.

According to another example embodiment, TOF analysis may be used toindirectly determine a physical distance from the capture device 120 toa particular location on the targets or objects by analyzing theintensity of the reflected beam of light over time via varioustechniques including, for example, shuttered light pulse imaging.

In another example embodiment, the capture device 120 may use astructured light to capture depth information. In such an analysis,patterned light (i.e., light displayed as a known pattern such as gridpattern, a stripe pattern, or different pattern) may be projected ontothe scene via, for example, the IR light component 224. Upon strikingthe surface of one or more targets or objects in the scene, the patternmay become deformed in response. Such a deformation of the pattern maybe captured by, for example, the 3-D camera 226 and/or the RGB camera228 and may then be analyzed to determine a physical distance from thecapture device to a particular location on the targets or objects. Insome implementations, the IR Light component 224 is displaced from thecameras 226 and 228 so triangulation can be used to determined distancefrom cameras 226 and 228. In some implementations, the capture device120 will include a dedicated IR sensor to sense the IR light.

According to another embodiment, the capture device 120 may include twoor more physically separated cameras that may view a scene fromdifferent angles to obtain visual stereo data that may be resolved togenerate depth information. Other types of depth image sensors can alsobe used to create a depth image.

The capture device 120 may further include a microphone 230. Themicrophone 230 may include a transducer or sensor that may receive andconvert sound into an electrical signal. According to one embodiment,the microphone 230 may be used to reduce feedback between the capturedevice 120 and the computing system 112 in the target recognition,analysis, and tracking system 100. Additionally, the microphone 230 maybe used to receive audio signals (e.g., voice commands) that may also beprovided by the user to control applications such as game applications,non-game applications, or the like that may be executed by the computingsystem 112.

In an example embodiment, the capture device 120 may further include aprocessor 232 that may be in operative communication with the imagecamera component 222. The processor 232 may include a standardizedprocessor, a specialized processor, a microprocessor, or the like thatmay execute instructions including, for example, instructions forreceiving a depth image, generating the appropriate data format (e.g.,frame) and transmitting the data to computing system 112.

The capture device 120 may further include a memory component 234 thatmay store the instructions that may be executed by the processor 232,images or frames of images captured by the 3-D camera and/or RGB camera,or any other suitable information, images, or the like. According to anexample embodiment, the memory component 234 may include random accessmemory (RAM), read only memory (ROM), cache, Flash memory, a hard disk,or any other suitable storage component. As shown in FIG. 2A, in oneembodiment, the memory component 234 may be a separate component incommunication with the image capture component 222 and the processor232. According to another embodiment, the memory component 234 may beintegrated into the processor 232 and/or the image capture component222.

As shown in FIG. 2A, the capture device 120 may be in communication withthe computing system 212 via a communication link 236. The communicationlink 236 may be a wired connection including, for example, a USBconnection, a Firewire connection, an Ethernet cable connection, or thelike and/or a wireless connection such as a wireless 802.11b, g, a, or nconnection. According to one embodiment, the computing system 112 mayprovide a clock to the capture device 120 that may be used to determinewhen to capture, for example, a scene via the communication link 236.Additionally, the capture device 120 provides the depth images and colorimages captured by, for example, the 3-D camera 226 and/or the RGBcamera 228 to the computing system 112 via the communication link 236.In one embodiment, the depth images and color images are transmitted at30 frames per second. The computing system 112 may then use the model,depth information, and captured images to, for example, control anapplication such as a game or word processor and/or animate an avatar oron-screen character.

Computing system 112 includes gestures library 240, structure data 242,depth image processing and object reporting module 244 and application246. Depth image processing and object reporting module 244 uses thedepth images to track motion of objects, such as the user and otherobjects. To assist in the tracking of the objects, depth imageprocessing and object reporting module 244 uses gestures library 240 andstructure data 242.

Structure data 242 includes structural information about objects thatmay be tracked. For example, a skeletal model of a human may be storedto help understand movements of the user and recognize body parts.Structural information about inanimate objects may also be stored tohelp recognize those objects and help understand movement.

Gestures library 240 may include a collection of gesture filters, eachcomprising information concerning a gesture that may be performed by theskeletal model (as the user moves). The data captured by the cameras226, 228 and the capture device 120 in the form of the skeletal modeland movements associated with it may be compared to the gesture filtersin the gesture library 240 to identify when a user (as represented bythe skeletal model) has performed one or more gestures. Those gesturesmay be associated with various controls of an application. Thus, thecomputing system 112 may use the gestures library 240 to interpretmovements of the skeletal model and to control application 246 based onthe movements. As such, gestures library may be used by depth imageprocessing and object reporting module 244 and application 246.

Application 246 can be a video game, productivity application, etc. Inone embodiment, depth image processing and object reporting module 244will report to application 246 an identification of each object detectedand the location of the object for each frame. Application 246 will usethat information to update the position or movement of an avatar orother images in the display.

FIG. 2B illustrates an example embodiment of a TOF type of 3-D camera226, which can also be referred to as a TOF camera 226, or moregenerally can be referred to as a TOF system 226. The TOF system 226 isshown as including a driver 260 that drives a light source 250. Thelight source 250 can be the IR light component 224 shown in FIG. 2A, orcan be one or more other light emitting element. More generally, thelight source 250 can include one or more light emitting elements, suchas, but not limited to, laser diodes or light emitting diodes (LEDs). Alaser diode can include one or more vertical-cavity surface-emittinglasers (VCESLs) or edge emitting lasers, but is not limited thereto. Itis also possible that there are multiple types of light sources, e.g., afirst light source including one or more laser diodes, and a secondlight source including one or more LEDs. While it is likely that suchlight emitting elements emit IR light, light of alternative wavelengthscan alternatively be emitted by the light emitting elements. Unlessstated otherwise, it is assumed that the light source 250 emits IRlight.

The TOF system 226 is also shown as including a clock signal generator262, which produces a clock signal that is provided to the driver 260.Additionally, the TOF system 226 is shown as including a microprocessor264 that can control the clock signal generator 262 and/or the driver260. The TOF system 226 is also shown as including an image pixeldetector array 268, readout circuitry 270 and memory 266. The imagepixel detector array 268 might include, e.g., 320×240 image pixeldetectors, but is not limited thereto. Each image pixel detector can be,e.g., a complementary metal-oxide-semiconductor (CMOS) sensor or acharged coupled device (CCD) sensor, but is not limited thereto.Depending upon implementation, each image pixel detector can have itsown dedicated readout circuit, or readout circuitry can be shared bymany image pixel detectors. In accordance with certain embodiments, thecomponents of the TOF system 226 shown within the block 280 areimplemented in a single integrated circuit (IC), which can also bereferred to as a single TOF chip.

The driver 260 can produce a radio frequency (RF) modulated drive signalin dependence on a clock signal received from clock signal generator262. Accordingly, the driver 260 can include, for example, one or morebuffers, amplifiers and/or modulators, but is not limited thereto. Theclock signal generator 262 can include, for example, one or morereference clocks and/or voltage controlled oscillators, but is notlimited thereto. The microprocessor 264, which can be part of amicrocontroller unit, can be used to control the clock signal generator262 and/or the driver 260. For example, the microprocessor 264 canaccess waveform information stored in the memory 266 in order to producean RF modulated drive signal in accordance with various embodimentsdescribed herein. The TOF system 226 can includes its own memory 266 andmicroprocessor 264, as shown in FIG. 2B. Alternatively, or additionally,the processor 232 and/or memory 234 of the capture device 120 can beused to control aspects of the TOF system 226.

In response to being driven by an RF modulated drive signal, the lightsource 250 emits RF modulated light, which can also be referred to as anRF modulate light signal. For an example, a carrier frequency of the RFmodulated drive signal and the RF modulated light can be in a range fromabout 5 MHz to many hundreds of MHz, but for illustrative purposes willbe assumed to be about 100 MHz. The light emitted by the light source250 is transmitted through an optional lens or light shaping diffuser252 towards a target object (e.g., a user 118). Assuming that there is atarget object within the field of view of the TOF camera, a portion ofthe RF modulated emitted light reflects off the target object, passesthrough an aperture field stop and lens (collectively 272), and isincident on the image pixel detector array 268 where an image is formed.In some implementations, each individual image pixel detector of thearray 268 produces an integration value indicative of a magnitude and aphase of detected RF modulated light originating from the light sourcethat has reflected off the object and is incident of the image pixeldetector. Such integrations values, or more generally TOF information,enable distances (Z) to be determined, and collectively, enable depthimages to be produced. In certain embodiments, optical energy from thelight source 250 and detected optical energy signals are synchronized toeach other such that a phase difference, and thus a distance Z, can bemeasured from each image pixel detector. The readout circuitry 270converts analog integration values generated by the image pixel detectorarray 268 into digital readout signals, which are provided to themicroprocessor 264 and/or the memory 266, and which can be used toproduce depth images.

FIG. 3 illustrates an example embodiment of a computing system that maybe the computing system 112 shown in FIGS. 1A-2B used to track motionand/or animate (or otherwise update) an avatar or other on-screen objectdisplayed by an application. The computing system such as the computingsystem 112 described above with respect to FIGS. 1A-2 may be amultimedia console, such as a gaming console. As shown in FIG. 3, themultimedia console 300 has a central processing unit (CPU) 301 having alevel 1 cache 102, a level 2 cache 304, and a flash ROM (Read OnlyMemory) 306. The level 1 cache 302 and a level 2 cache 304 temporarilystore data and hence reduce the number of memory access cycles, therebyimproving processing speed and throughput. The CPU 301 may be providedhaving more than one core, and thus, additional level 1 and level 2caches 302 and 304. The flash ROM 306 may store executable code that isloaded during an initial phase of a boot process when the multimediaconsole 300 is powered ON.

A graphics processing unit (GPU) 308 and a video encoder/video codec(coder/decoder) 314 form a video processing pipeline for high speed andhigh resolution graphics processing. Data is carried from the graphicsprocessing unit 308 to the video encoder/video codec 314 via a bus. Thevideo processing pipeline outputs data to an A/V (audio/video) port 340for transmission to a television or other display. A memory controller310 is connected to the GPU 308 to facilitate processor access tovarious types of memory 312, such as, but not limited to, a RAM (RandomAccess Memory).

The multimedia console 300 includes an I/O controller 320, a systemmanagement controller 322, an audio processing unit 323, a networkinterface 324, a first USB host controller 326, a second USB controller328 and a front panel I/O subassembly 330 that are preferablyimplemented on a module 318. The USB controllers 326 and 328 serve ashosts for peripheral controllers 342(1)-342(2), a wireless adapter 348,and an external memory device 346 (e.g., flash memory, external CD/DVDROM drive, removable media, etc.). The network interface 324 and/orwireless adapter 348 provide access to a network (e.g., the Internet,home network, etc.) and may be any of a wide variety of various wired orwireless adapter components including an Ethernet card, a modem, aBluetooth module, a cable modem, and the like.

System memory 343 is provided to store application data that is loadedduring the boot process. A media drive 344 is provided and may comprisea DVD/CD drive, Blu-Ray drive, hard disk drive, or other removable mediadrive, etc. The media drive 344 may be internal or external to themultimedia console 300. Application data may be accessed via the mediadrive 344 for execution, playback, etc. by the multimedia console 300.The media drive 344 is connected to the I/O controller 320 via a bus,such as a Serial ATA bus or other high speed connection (e.g., IEEE1394).

The system management controller 322 provides a variety of servicefunctions related to assuring availability of the multimedia console300. The audio processing unit 323 and an audio codec 332 form acorresponding audio processing pipeline with high fidelity and stereoprocessing. Audio data is carried between the audio processing unit 323and the audio codec 332 via a communication link. The audio processingpipeline outputs data to the A/V port 340 for reproduction by anexternal audio player or device having audio capabilities.

The front panel I/O subassembly 330 supports the functionality of thepower button 350 and the eject button 352, as well as any LEDs (lightemitting diodes) or other indicators exposed on the outer surface of themultimedia console 300. A system power supply module 336 provides powerto the components of the multimedia console 300. A fan 338 cools thecircuitry within the multimedia console 300.

The CPU 301, GPU 308, memory controller 310, and various othercomponents within the multimedia console 300 are interconnected via oneor more buses, including serial and parallel buses, a memory bus, aperipheral bus, and a processor or local bus using any of a variety ofbus architectures. By way of example, such architectures can include aPeripheral Component Interconnects (PCI) bus, PCI-Express bus, etc.

When the multimedia console 300 is powered ON, application data may beloaded from the system memory 343 into memory 312 and/or caches 302, 304and executed on the CPU 301. The application may present a graphicaluser interface that provides a consistent user experience whennavigating to different media types available on the multimedia console300. In operation, applications and/or other media contained within themedia drive 344 may be launched or played from the media drive 344 toprovide additional functionalities to the multimedia console 300.

The multimedia console 300 may be operated as a standalone system bysimply connecting the system to a television or other display. In thisstandalone mode, the multimedia console 300 allows one or more users tointeract with the system, watch movies, or listen to music. However,with the integration of broadband connectivity made available throughthe network interface 324 or the wireless adapter 348, the multimediaconsole 300 may further be operated as a participant in a larger networkcommunity.

When the multimedia console 300 is powered ON, a set amount of hardwareresources are reserved for system use by the multimedia consoleoperating system. These resources may include a reservation of memory(e.g., 16 MB), CPU and GPU cycles (e.g., 5%), networking bandwidth(e.g., 8 Kbps), etc. Because these resources are reserved at system boottime, the reserved resources do not exist from the application's view.

In particular, the memory reservation preferably is large enough tocontain the launch kernel, concurrent system applications and drivers.The CPU reservation is preferably constant such that if the reserved CPUusage is not used by the system applications, an idle thread willconsume any unused cycles.

With regard to the GPU reservation, lightweight messages generated bythe system applications (e.g., popups) are displayed by using a GPUinterrupt to schedule code to render popup into an overlay. The amountof memory required for an overlay depends on the overlay area size andthe overlay preferably scales with screen resolution. Where a full userinterface is used by the concurrent system application, it is preferableto use a resolution independent of application resolution. A scaler maybe used to set this resolution such that the need to change frequencyand cause a TV resynch is eliminated.

After the multimedia console 300 boots and system resources arereserved, concurrent system applications execute to provide systemfunctionalities. The system functionalities are encapsulated in a set ofsystem applications that execute within the reserved system resourcesdescribed above. The operating system kernel identifies threads that aresystem application threads versus gaming application threads. The systemapplications are preferably scheduled to run on the CPU 301 atpredetermined times and intervals in order to provide a consistentsystem resource view to the application. The scheduling is to minimizecache disruption for the gaming application running on the console.

When a concurrent system application requires audio, audio processing isscheduled asynchronously to the gaming application due to timesensitivity. A multimedia console application manager (described below)controls the gaming application audio level (e.g., mute, attenuate) whensystem applications are active.

Input devices (e.g., controllers 342(1) and 342(2)) are shared by gamingapplications and system applications. The input devices are not reservedresources, but are to be switched between system applications and thegaming application such that each will have a focus of the device. Theapplication manager preferably controls the switching of input stream,without knowledge the gaming application's knowledge and a drivermaintains state information regarding focus switches. The cameras 226,228 and capture device 120 may define additional input devices for theconsole 300 via USB controller 326 or other interface.

FIG. 4 illustrates another example embodiment of a computing system 420that may be the computing system 112 shown in FIGS. 1A-2B used to trackmotion and/or animate (or otherwise update) an avatar or other on-screenobject displayed by an application. The computing system 420 is only oneexample of a suitable computing system and is not intended to suggestany limitation as to the scope of use or functionality of the presentlydisclosed subject matter. Neither should the computing system 420 beinterpreted as having any dependency or requirement relating to any oneor combination of components illustrated in the exemplary computingsystem 420. In some embodiments the various depicted computing elementsmay include circuitry configured to instantiate specific aspects of thepresent disclosure. For example, the term circuitry used in thedisclosure can include specialized hardware components configured toperform function(s) by firmware or switches. In other examplesembodiments the term circuitry can include a general purpose processingunit, memory, etc., configured by software instructions that embodylogic operable to perform function(s). In example embodiments wherecircuitry includes a combination of hardware and software, animplementer may write source code embodying logic and the source codecan be compiled into machine readable code that can be processed by thegeneral purpose processing unit. Since one skilled in the art canappreciate that the state of the art has evolved to a point where thereis little difference between hardware, software, or a combination ofhardware/software, the selection of hardware versus software toeffectuate specific functions is a design choice left to an implementer.More specifically, one of skill in the art can appreciate that asoftware process can be transformed into an equivalent hardwarestructure, and a hardware structure can itself be transformed into anequivalent software process. Thus, the selection of a hardwareimplementation versus a software implementation is one of design choiceand left to the implementer.

Computing system 420 comprises a computer 441, which typically includesa variety of computer readable media. Computer readable media can be anyavailable media that can be accessed by computer 441 and includes bothvolatile and nonvolatile media, removable and non-removable media. Thesystem memory 422 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 423and random access memory (RAM) 460. A basic input/output system 424(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 441, such as during start-up, istypically stored in ROM 423. RAM 460 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 459. By way of example, and notlimitation, FIG. 4 illustrates operating system 425, applicationprograms 426, other program modules 427, and program data 428.

The computer 441 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 4 illustrates a hard disk drive 438 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 439that reads from or writes to a removable, nonvolatile magnetic disk 454,and an optical disk drive 440 that reads from or writes to a removable,nonvolatile optical disk 453 such as a CD ROM or other optical media.Other removable/non-removable, volatile/nonvolatile computer storagemedia that can be used in the exemplary operating environment include,but are not limited to, magnetic tape cassettes, flash memory cards,digital versatile disks, digital video tape, solid state RAM, solidstate ROM, and the like. The hard disk drive 438 is typically connectedto the system bus 421 through an non-removable memory interface such asinterface 434, and magnetic disk drive 439 and optical disk drive 440are typically connected to the system bus 421 by a removable memoryinterface, such as interface 435.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 4, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 441. In FIG. 4, for example, hard disk drive 438 is illustratedas storing operating system 458, application programs 457, other programmodules 456, and program data 455. Note that these components can eitherbe the same as or different from operating system 425, applicationprograms 426, other program modules 427, and program data 428. Operatingsystem 458, application programs 457, other program modules 456, andprogram data 455 are given different numbers here to illustrate that, ata minimum, they are different copies. A user may enter commands andinformation into the computer 441 through input devices such as akeyboard 451 and pointing device 452, commonly referred to as a mouse,trackball or touch pad. Other input devices (not shown) may include amicrophone, joystick, game pad, satellite dish, scanner, or the like.These and other input devices are often connected to the processing unit459 through a user input interface 436 that is coupled to the systembus, but may be connected by other interface and bus structures, such asa parallel port, game port or a universal serial bus (USB). The cameras226, 228 and capture device 120 may define additional input devices forthe computing system 420 that connect via user input interface 436. Amonitor 442 or other type of display device is also connected to thesystem bus 421 via an interface, such as a video interface 432. Inaddition to the monitor, computers may also include other peripheraloutput devices such as speakers 444 and printer 443, which may beconnected through a output peripheral interface 433. Capture Device 120may connect to computing system 420 via output peripheral interface 433,network interface 437, or other interface.

The computer 441 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer446. The remote computer 446 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 441, although only a memory storage device 447 has beenillustrated in FIG. 4. The logical connections depicted include a localarea network (LAN) 445 and a wide area network (WAN) 449, but may alsoinclude other networks. Such networking environments are commonplace inoffices, enterprise-wide computer networks, intranets and the Internet.

When used in a LAN networking environment, the computer 441 is connectedto the LAN 445 through a network interface 437. When used in a WANnetworking environment, the computer 441 typically includes a modem 450or other means for establishing communications over the WAN 449, such asthe Internet. The modem 450, which may be internal or external, may beconnected to the system bus 421 via the user input interface 436, orother appropriate mechanism. In a networked environment, program modulesdepicted relative to the computer 441, or portions thereof, may bestored in the remote memory storage device. By way of example, and notlimitation, FIG. 4 illustrates application programs 448 as residing onmemory device 447. It will be appreciated that the network connectionsshown are exemplary and other means of establishing a communicationslink between the computers may be used.

As explained above, the capture device 120 provides RGB images (alsoknown as color images) and depth images to the computing system 112. Thedepth image may be a plurality of observed pixels where each observedpixel has an observed depth value. For example, the depth image mayinclude a two-dimensional (2-D) pixel area of the captured scene whereeach pixel in the 2-D pixel area may have a depth value such as a lengthor distance in, for example, centimeters, millimeters, or the like of anobject in the captured scene from the capture device.

FIG. 5 illustrates an example embodiment of a depth image that may bereceived at computing system 112 from capture device 120. According toan example embodiment, the depth image may be an image and/or frame of ascene captured by, for example, the 3-D camera 226 and/or the RGB camera228 of the capture device 120 described above with respect to FIG. 2A.As shown in FIG. 5, the depth image may include a human targetcorresponding to, for example, a user such as the user 118 describedabove with respect to FIGS. 1A and 1B and one or more non-human targetssuch as a wall, a table, a monitor, or the like in the captured scene.The depth image may include a plurality of observed pixels where eachobserved pixel has an observed depth value associated therewith. Forexample, the depth image may include a two-dimensional (2-D) pixel areaof the captured scene where each pixel at particular x-value and y-valuein the 2-D pixel area may have a depth value such as a length ordistance in, for example, centimeters, millimeters, or the like of atarget or object in the captured scene from the capture device. In otherwords, a depth image can specify, for each of the pixels in the depthimage, a pixel location and a pixel depth. Following a segmentationprocess, each pixel in the depth image can also have a segmentationvalue associated with it. The pixel location can be indicated by anx-position value (i.e., a horizontal value) and a y-position value(i.e., a vertical value). The pixel depth can be indicated by az-position value (also referred to as a depth value), which isindicative of a distance between the capture device (e.g., 120) used toobtain the depth image and the portion of the user represented by thepixel. The segmentation value is used to indicate whether a pixelcorresponds to a specific user, or does not correspond to a user.

In one embodiment, the depth image may be colorized or grayscale suchthat different colors or shades of the pixels of the depth imagecorrespond to and/or visually depict different distances of the targetsfrom the capture device 120. Upon receiving the image, one or morehigh-variance and/or noisy depth values may be removed and/or smoothedfrom the depth image; portions of missing and/or removed depthinformation may be filled in and/or reconstructed; and/or any othersuitable processing may be performed on the received depth image.

FIG. 6 provides another view/representation of a depth image (notcorresponding to the same example as FIG. 5). The view of FIG. 6 showsthe depth data for each pixel as an integer that represents the distanceof the target to capture device 120 for that pixel. The example depthimage of FIG. 6 shows 24×24 pixels; however, it is likely that a depthimage of greater resolution would be used.

Techniques for Reducing IR Remote Control Interference Caused by TOFSystems

As mentioned above, a TOF system (e.g., 226) may be located in closeproximity to (e.g., within the same room as) a consumer electronicdevice (e.g., a television, a set top box and/or a media player) thatis/are configured to be remotely controlled by a handheld remote controldevice. For example, referring back to FIGS. 1A and 2A, the capturedevice 120 can include a TOF system 226 that is located close to thetelevision or display 116. Additionally, or alternatively, a TOF systemmay be located in close proximity to other types of systems configuredto wirelessly receive and respond to IR light signals, such as, but notlimited to, systems that include wireless IR headphones and 3Dtelevision systems that include active shutter 3D glasses. As alsoexplained above, the TOF system may operate by illuminating a target(e.g., user 118) with RF modulated IR light and detecting IR light thatreflects off the target and is incident on an image pixel detector arrayof the TOF camera. While the carrier frequency of the RF modulated IRlight is typically well above the carrier frequency of remote controlsignals, abrupt transitions from times during which the light sourcedoes not emit the RF modulated light to times during which the lightsource emits RF modulated light, and vice versa, can produce lowerfrequency content that can interfere with the remote control signals.Explained another way, a low frequency content associated with themodulated IR light, produced by the TOF system, may interfere withremote control signals intended to control another device (e.g., atelevision) within the vicinity of the TOF system. While most if not allof the interference produced by the TOF system will not correspond to avalid remote control command (and thus, will be rejected by a remotecontrol receiver of the other device as an invalid command), theinterference produced by the TOF system may be significant enough toprevent a user from being able to actually remotely control the otherdevice (e.g., the television or display 116) that is within closeproximity to the TOF system. The low frequency content produced by theTOF system can similarly interference with other types of systems thatare configured to wirelessly receive and respond to IR light signals.Certain embodiments of the present technology described below, which arefor use with a TOF system, substantially reduce frequency content withinthe range of frequencies known to be used by remote control devicesand/or within one or more other frequency ranges known to be used byother systems configured to wirelessly receive and respond to IR lightsignals. Accordingly, such embodiments enable other systems to operatein their intended manner when in close proximity to a TOF system. For amore specific example, such embodiments enable consumer electronicdevices to be remotely controlled even though they are in closeproximity to a TOF system.

Most, IR remote control signals have a carrier frequency between 10 kHzand 100 kHz, and even more specifically between 30 kHz and 60 kHz.Certain remote control devices, for example, transmit IR remote controlsignals having a carrier frequency of about 36 kHz (this is not to beconfused with the actual frequency of the IR light itself). There arealso some systems that utilize IR remote control signals having acarrier frequency of about 455 KHz. Still other systems utilize IRremote control signals having a carrier frequency of about 1 MHz. Aconsumer electronic device (e.g., television, set top box or mediaplayer) that is controllable by remote control signals includes a remotecontrol receiver that is configured to receive and decode remote controlsignals within an expected frequency range, examples of which werediscussed above.

Before describing various embodiments of the present technology, FIG. 7will first be used to describe a typical RF modulated drive signalgenerated by a TOF system and a typical RF modulated IR light signalemitted by the TOF system. More specifically, FIG. 7 illustratesexemplary pulse timing and pulse amplitude details associated with twoexemplary frames of signals for use with a TOF system. The frames shownin FIG. 7 can be for use with a TOF system that, for example, isconfigured to obtain a separate depth image corresponding to each of aplurality of frames, which can also be referred to as frame periods. Thewaveforms shown in FIG. 7 are illustrative of both an RF modulated drivesignal used to drive an IR light source, as well as an RF modulated IRlight signal produced by (and more specifically, emitted by) the lightsource being driven by the RF modulated drive signal.

As shown in FIG. 7, each frame period is followed by an inter-frameperiod, which separates the frame period from the next frame period.Depending upon implementation, the length of each frame period may ormay not be the same as the length of each inter-frame period. Each frameperiod includes at least two integration periods, and each integrationperiod is followed by a readout period. For a more specific example, aframe period may include ten integration periods, each of which isfollowed by a respective one of ten readout periods. Except for the lastreadout period of a frame period, each of the readout periods separatesa pair of the integration periods of the frame period. The frame ratecan be, for example, 30 Hz, but is not limited thereto. Where the framerate is 30 Hz, each frame period plus inter-frame period pair is about33.33 msec.

Still referring to FIG. 7, each of the integration periods is shown asincluding numerous pulses having the same pulse amplitude, and each ofthe readout periods and inter-frame periods is shown as including nopulses. As mentioned above, FIG. 7 is illustrative of an RF modulateddrive signal, as well as the RF modulated IR light signal generated bydriving an IR light source with the RF modulated drive signal. Assumingthat the pulse frequency is about 100 MHz, the pulse frequency is wellabove the frequency range known to be used by most other systems thatare configured to wirelessly receive and respond to IR light signals.Nevertheless, the LF power envelope of the RF modulated IR lightincludes significant frequency content within the frequency ranges knownto be used by other systems that are configured to wirelessly receiveand respond to IR light signal, examples of which were discussed above.Such frequency content is primarily due to the abrupt transitions fromtimes during which the light source is not driven by the RF modulateddrive signal to times during which the light source is driven by the RFmodulated drive signal, and vice versa, which occur at the beginning andend of each of the integration periods. The shaded areas labeled 702 inFIG. 7 are illustrative of the LF power envelopes of the RF modulateddrive signal and the RF modulated light signal produced using the drivesignal. A LF power envelope, as the term is used herein, is the LFaverage power delivered over time by a signal.

FIG. 8 illustrates an exemplary LF frequency power spectrum associatedwith the signal shown in FIG. 7. As can be appreciated from FIG. 8,there is significant frequency content within the 10 kHz to 100 kHzfrequency range known to be used by remote control devices. It is thisspectral energy produced by a TOF system that results, for example, ininterference that may prevent a system (e.g., a television or display)within close proximity to the TOF system from being remotely controlledusing IR remote control signals. Although not shown in FIG. 8, sinceFIG. 8 only shows LF content, the power spectrum associated with thesignal shown in FIG. 7 will also include a peak at the carrierfrequency, e.g., at 100 MHz.

Certain embodiments of the present technology, which are describedbelow, smooth out the edges of the LF power envelopes of the drive andIR light signals. This has the effect of substantially reducingfrequency content within the frequency ranges known to be used by remotecontrolled devices and other systems configured to wirelessly receiveand respond to IR light signals.

A first embodiment for smoothing out the edges of the LF powerenvelopes, which is illustrated in FIG. 9, involves ramping up the pulseamplitudes of an RF component of a drive signal when transitioning froma time during which no light source is driven to emit IR light to a timeduring which a light source is driven by the drive signal to emit IRlight. This embodiment also includes ramping down pulse amplitudes ofthe RF component of the drive signal when transitioning from a timeduring which a light source is driven by the drive signal to emit IRlight to a time during which no light source is driven to emit IR light.By driving the light source with the drive signal having pulseamplitudes that ramp up and thereafter ramp down, the RF component ofthe IR light signal emitted by the light source will also have pulseamplitudes that ramp up and thereafter ramp down. The shaded areaslabeled 902 in FIG. 9 are illustrative of the LF power envelopes of thedrive signal and the IR light signal produced using the drive signal.The ramping up of the pulse amplitudes should occur over a period of atleast 50 μsec and the ramping down of the pulse amplitudes should occurover a period of at least 50 μsec. Time permitting, the ramping up ofthe pulse amplitudes preferably occurs over a period betweenapproximately 1 msec and 10 msec, and the ramping down similarlypreferably occurs over a period between approximately 1 msec and 10msec, which should ensure a substantial reduction in frequency contentbetween 10 kHz and 100 kHz, which is the frequency range typically usedto transmit IR remote control signals. It is noted that FIG. 9 isincluded for illustrative purposes, but is not drawn to scale, since theramping up and down of pulse amplitudes will occur over much more thanthree or four pulses.

There are various different ways to implement the embodiment describedwith reference to FIG. 9. For example, referring back to FIG. 2B, themicroprocessor 264 can control the clock signal generator 262 to produceclock pulses having pulse amplitudes that ramp up and ramp down.Alternatively, the microprocessor 264 can control the driver 260 toproduce an RF modulated drive signal that includes pulse amplitudes thatramp up and ramp down. For example, the driver 260 can include a pulseamplitude modulator that is controlled by the microprocessor 264. Themicroprocessor 264 may access information regarding pulse amplitudesfrom the memory 266. Such a pulse amplitude modulator can beimplemented, e.g., using an amplifier having an adjustable gain that iscontrolled by the microcontroller. These are just a few examples, whichare not meant to be all encompassing.

A second embodiment for smoothing out the edges of the LF powerenvelopes, which is illustrated in FIG. 10, involves ramping up thepulse duty cycles of an RF component of the drive signal whentransitioning from a time during which no light source is driven to emitIR light to a time during which a light source is driven by the drivesignal to emit IR light. This embodiment also includes ramping downpulse duty cycles of the RF component of the drive signal whentransitioning from a time during which the light source is driven by thedrive signal to emit IR light to a time during which no light source isdriven to emit IR light. By driving the light source with the drivesignal having pulse duty cycles that ramp up and thereafter ramp down,the RF component of the light signal emitted by the light source willalso have pulse duty cycles that ramp up and thereafter ramp down. Theshaded areas labeled 1002 in FIG. 10 are illustrative of the LF powerenvelopes of the drive signal and the IR light signal produced using thedrive signal. The ramping up of the pulse duty cycles should occur overa period of at least 50 μsec and the ramping down of the pulse dutycycles should occur over a period of at least 50 μsec. Time permitting,the ramping up of the pulse duty cycles preferably occurs over a periodbetween approximately 1 msec and 10 msec, and the ramping down similarlyoccurs over a period between approximately 1 msec and 10 msec, whichshould ensure a substantial reduction in frequency content between 10kHz and 100 kHz, which is the frequency range typically used to transmitIR remote control signals. It is noted that FIG. 10 is included forillustrative purposes, but is not drawn to scale, since the ramping upand down of pulse duty cycles will occur over much more than three orfour pulses.

There are various different ways to implement the embodiment describedwith reference to FIG. 10. For example, referring back to FIG. 2B, themicroprocessor 264 can control the clock signal generator 262 to produceclock pulses having pulse duty cycles that ramp up and ramp down.Alternatively, the microprocessor 264 can control the driver 260 toproduce a drive signal having an RF component that includes pulse dutycycles that ramp up and ramp down. For example, the driver 260 caninclude a pulse duty cycle modulator that is controlled by themicroprocessor 264. The microprocessor 264 may access informationregarding pulse duty cycles from the memory 266. Such a pulse duty cyclemodulator can be implemented, e.g., using a pulse width modulator. Theseare just a few examples, which are not meant to be all encompassing.

Another embodiment for smoothing out the edges of the LF powerenvelopes, which is illustrated in FIG. 11, involves ramping downtemporal gaps between adjacent pulses or pulse trains of the RFmodulated drive signal when transitioning from a time during which nolight source is driven to emit IR light to a time during which a lightsource is driven by the drive signal to emit IR light. This embodimentalso includes ramping up temporal gaps between adjacent pulses or pulsetrains of the RF component of the drive signal when transitioning from atime during which a light source is driven by the drive signal to emitIR light to a time during which no light source is driven to emit IRlight. By driving the light source with the drive signal including an RFcomponent having temporal gaps between adjacent pulses or pulse trainsthat ramp down and thereafter ramp up, the RF component of the IR lightsignal emitted by the light source will also have pulses or pulse trainswith temporal gaps that ramp down and thereafter ramp up. The shadedareas labeled 1102 in FIG. 11 are illustrative of the LF power envelopesof the drive signal and the light signal produced using the drivesignal. The ramping down of the temporal gaps between adjacent pulses orpulse trains should occur over a period of at least 50 μsec and theramping down of the temporal gaps between adjacent pulses or pulsetrains should occur over a period of at least 50 μsec. Time permitting,the ramping down of the temporal gaps between adjacent pulses or pulsetrains preferably occurs over a period between approximately 1 msec and10 msec, and the ramping up of the temporal gaps between adjacent pulsesor pulse trains similarly preferably occurs over a period betweenapproximately 1 msec and 10 msec, which should ensure a substantialreduction in frequency content between 10 kHz and 100 kHz, which is thefrequency range typically used to transmit IR remote control signals. Itis noted that FIG. 11 is included for illustrative purposes, but is notdrawn to scale, since the ramping down and up of temporal gaps betweenadjacent pulses will occur over much more than three or four pulses.Alternatively, or additionally, there can be a ramping down of how oftengaps occur between pulses or pulse trains of a drive signal whentransitioning from a time during which no light source is driven to emitIR light to a time during which a light source is driven by the drivesignal to emit IR light; and there can be a ramping up of how often gapsoccur between pulses or pulse trains of the drive signal whentransitioning from a time during which a light source is driven by thedrive signal to emit IR light to a time during which no light source isdrive to emit IR light.

There are various different ways to implement the embodiment describedwith reference to FIG. 11. For example, referring back to FIG. 2B, themicroprocessor 264 can control the clock signal generator 262 to produceclock pulses having temporal gaps between pulses that that ramp down andramp up. This can be accomplished, e.g., by not outputting certain clockpulses. Alternatively, a gating circuit can be located between the clocksignal generator 262 and the driver 260, so that some clock pulses arenot provided to the driver 260, to thereby control the temporal gapsbetween adjacent pulses or pulse trains, and/or how often gaps occur. Instill another embodiment, the gating circuit can be part of or upstreamfrom the driver 260 and can selectively prevent some drive pulses frombeing provided to the light source 250, to thereby control the temporalgaps between adjacent pulses or pulse trains output by the light sourceand/or how often gaps occur. The microprocessor 264 can control theclock signal generator 262, the driver 260 and/or such a gating circuitto achieve the ramping up and down of temporal gaps between pulses orpulse trains, and/or how often gaps occur. The microprocessor 264 mayaccess information regarding temporal gaps and/or how often gaps shouldoccur between pulses or pulse trains from the memory 266. These are justa few examples, which are not meant to be all encompassing.

As mentioned above, the abrupt transitions from times during which alight source emits IR light to times during which no light source emitsIR light, and vice versa, produces frequency content that can interferewith the IR remote control signals and/or other IR signals used by othersystems. As also mentioned above, explained another way, the LF powerenvelopes associated with the IR light, produced by the TOF camera, mayinterfere with one or more other system (configured to wirelesslyreceive and respond to IR light signals) that is/are within closeproximity to the TOF camera. An embodiment, which will now be describedwith reference to FIG. 12, reduces how often there are transitions fromtimes during which IR light is emitted to times during which IR light isnot emitted, and vice versa, thereby reducing frequency contentassociated with such transitions.

Typically, the RF modulated drive and RF modulated light signals areonly produced during the integration periods of frame periods, but arenot produced during the readout periods of frame periods, as was shownin FIGS. 7 and 9-11. In accordance with an embodiment, drive and IRlight signals are produced during each of the integration periods ofeach frame period as well as during each of the readout periods betweenpairs of the integration periods within each frame period, as shown inFIG. 12. This has the effect of reducing how often there are transitionsfrom times during which no light source emits IR light to times duringwhich a light source is driven to emit IR light, and vice versa, andthereby reduces frequency content associated with such transitions. Theshaded areas labeled 1202 in FIG. 12 are illustrative of the LF powerenvelopes of the drive and IR light signals produced using such anembodiment. As can be appreciated from FIG. 12, even though there aremultiple integration and readout periods per frame period, there is onlyone LF power envelope per frame period, and thus only one rising edge ofthe LF power envelope and only one falling edge of the LF powerenvelope. In other words, during each frame period, there is only onetransition from a time during which no light source emits IR light to atime during which a light source is driven by the drive signal to emitIR light; and there is only one transition from a time during which alight source is driven to emit IR light to a time during which no lightsource emits IR light. The same light source can be used for emitting IRlight during integration periods and readout periods. Alternatively, afirst light source (e.g., an IR laser diode) can be used to emit IRlight during the integration periods, and a second light source (e.g.,an IR LED) can be used to emit IR light during the readout periods.Other variations are also possible, and within the scope of anembodiment.

The rising and falling edges of the LF power envelope 1202 in FIG. 12are abrupt, which will result in at least some frequency content withinthe frequency range known to be used by remote controlled devices andother systems configured to wirelessly receive and respond to IR lightsignals. To further reduce such frequency content, the embodiment justdescribed with reference to FIG. 12 can be combined with at least one ofthe previously described embodiments discussed with reference to FIGS.9-11. For example, FIG. 13 illustrates an embodiment that combines theembodiment described with reference to FIG. 12 with the embodimentdescribed with reference to FIG. 9. The shaded areas labeled 1302 inFIG. 13 are illustrative of the LF power envelopes of the drive signaland the emitted IR light signal produced using such an embodiment. Ascan be appreciated from FIG. 13, there is only one LF power envelope1302 per frame period, and thus only one rising edge of the LF powerenvelope and only one falling edge of the LF power envelope.Additionally, the rising and falling edges of the LF power envelope 1302in FIG. 13 are smoothed out. Thus, the embodiment described withreference to FIG. 13 achieves the benefits of the embodiment describedwith reference to FIG. 12 as well as the benefits of the embodimentdescribed with reference to FIG. 9. Alternatively, the embodimentdescribed with reference to FIG. 12 can be combined with one of theembodiments described with reference to FIG. 10 or 11 to achieve similarsubstantial reductions in frequency content within the frequency rangeknown to be used by remote controlled devices and other systemsconfigured to wirelessly receive and respond to IR light signals.

The embodiments described above can also be combined in other manners.For example, the embodiment described with reference to FIG. 9 can becombined with one or more of the embodiments described with reference toFIGS. 10 and 11. It is also possible that the embodiment described withreference to FIG. 12 can be combined with more than one of theembodiments described with reference to FIGS. 9-11.

In accordance with certain embodiments, where IR light signals are alsoemitted during readout periods, the readout circuitry (e.g., 270 in FIG.2B) either does not generate readout signals corresponding to reflectedlight detected by the image pixel detector array 268 during readoutperiods, or readout signals corresponding to reflected light detected bythe image pixel detector array 268 during readout periods should beignored by the TOF system. In accordance with alternative embodiments,in order to improve the overall electrical efficiency of the TOF system,the readout circuitry (e.g., 270 in FIG. 2B) generates, and the TOFsystem utilizes, the readout signals corresponding to reflected IR lightdetected by the image pixel detector array 268 during readout periods.

Many systems (e.g., televisions or set top boxes) that are configured towireless receive and respond to IR signals include a receiver that hasan automatic gain control (AGC) circuit that adjusts the sensitivity ofthe receiver in dependence on ambient light conditions. Morespecifically, such AGC circuits usually decrease gain of a receiveramplifier when there is high ambient light conditions, which makes thereceiver less sensitive; and the AGC circuits usually increase the gainof the receiver amplifier when where there is low ambient lightconditions, which makes the receiver more sensitive. The more sensitivethe receiver, the less need for a direct line of sight between asub-system that transmit IR signals (e.g., a remote control device thattransmits IR remote control signals) and the receiver, which forexample, can be built into a television or set top box. Conversely, theless sensitive the receiver, the more need for a direct line of sightbetween the sub-system (e.g., a remote control device that transmits IRremote control signals) and the receiver. The reason for reducing theamplifier gain during high ambient light conditions is that thereduction in gain makes the receiver less sensitive to interferenceresulting from ambient light. Experiments have shown that reducing thegain of a receiver amplifier also has the effect of making the receiverless sensitive to interference resulting from RF component of IR lightproduced by a TOF system. An embodiment of the present technology, whichshall now be described with reference to FIG. 14, purposely reduces thereceiver amplifier gain (even during low ambient light conditions) inorder to make a receiver (e.g., a remote control receiver) lesssensitive to interference resulting from IR light produced by a TOFsystem.

The AGC circuit of a receiver may, for example, have about 50 dB ofadjustable gain. Such an AGC circuit automatically varies the gain of areceiver amplifier between its minimum gain (in a bright environment)and its maximum gain (in a dark environment). In accordance with anembodiments, in order to decrease the sensitivity of an AGC circuit ofanother system (e.g., a system that is configured to wirelessly receiveand respond to IR remote control signals) and thereby make the othersystem less susceptible to interference from the TOF system, the driver(e.g., 250) of a TOF system drives a light source (e.g., 250) of the TOFsystem to cause IR light to also be emitted during the readout periodsbetween pairs of the integration periods within each frame period andduring at least a portion of the inter-frame periods between pairs offrames. In other words, the TOF system purposely increases thepercentage of each frame period during with IR light is emitted, asshown in FIG. 14. This causes an AGC circuit of another system (e.g., atelevision) within close proximity to the TOF system to reduce its levelof gain, making the receiver of the other system less susceptible tointerference from the TOF system. As can be appreciated from FIG. 14,the width of the LF power envelope 1402 can be made greater than thewidth of the frame period by emitting IR light during portions of theadjacent inter-frame periods. In other words, the TOF system may emit IRlight during at least of portion of inter-frame periods, which is nottypically done. As can be appreciated from FIG. 14, this embodiment canbe combined with previously described embodiments. For example, in FIG.14, the pulse amplitudes are ramped up and down in the manner originallydescribed with reference to FIG. 9 to smooth out the LF power envelope;and the pulses are also generated during readout periods to reduce thenumber of LF power envelope transitions as was originally described withreference to FIG. 12. The same light source can be used for emitting IRlight during integration periods, the readout periods and portions ofthe inter-frame periods. Alternatively, a first light source (e.g., anIR laser diode) can be used to emit IR light during the integrationperiods, and a second light source (e.g., an IR LED) can be used to emitIR light during the readout periods and portions of the inter-frameperiods. Other variations are also possible, and within the scope of anembodiment.

In FIGS. 9-14, the pulse amplitudes within the middle integrationperiod(s) of a frame period were shown as staying the same. However,this need not be the case. For example, the pulse amplitudes may changefrom one integration period to the next. In order to reduce frequencycontent resulting from such abrupt relatively significant changes inpulse amplitudes, it is advantageous to produce RF modulated drive andRF modulated light signals during the readout periods (between suchintegration periods) and smooth out the changes in the pulse amplitudes,as can be appreciated from FIG. 15. More generally, FIG. 15 illustratesa smoothing out of all transitions of the LF power envelope 1502. Theembodiment described with reference to FIG. 15 can be combined with oneor more of the previously described embodiments. For example, instead oframping up and down pulse amplitude to smooth out the LF power envelope1502, ramping up and down of pulse duty cycles, temporal gaps and/or howoften gaps occur between adjacent pulses or pulse trains can be used tosmooth out the LF power envelope 1502.

The high level flow diagram of FIG. 16 will now be used to summarizemethods according to various embodiments of the present technology. Suchmethods, which are for use by a TOF system, are for substantiallyreducing interference that the TOF system may cause to a further devicethat is configured to wirelessly receive and respond to IR signalstransmitted by a remote control device that is intended to remotelycontrol the further device (e.g., a television).

Referring to FIG. 16, step 1602 involves emitting IR light having a LFpower envelope that is shaped to substantially reduce frequency contentwithin at least one frequency range known to be used by at least oneother system configured to wirelessly receive and respond to IR lightsignals, wherein at least a portion of IR light being emitted is RFmodulated IR light. Frequency ranges within which frequency content canbe reduced using embodiments described herein include, but are notlimited to: 10 kHz-100 kHz frequencies that are used by some systems forsending IR remote control signals; 455 kHz (+/−10%) and/or 1 MHz(+/−10%) frequencies that are used by other systems for sending IRremote control signals; 2.3 MHz (+/−10%) and 2.8 MHz (+/−10%)frequencies that are used by some systems for transmitting IR signals towireless IR headphones; and 25 KHz-30 KHz frequencies that are used bysome systems for transmitting IR signals to wireless 3D shutter glasses.

Still referring to FIG. 16, step 1604 involves detecting at least aportion of the emitted RF modulated IR light that has reflected off oneor more objects. At step 1606, depth images are produced in dependenceon results of the detecting. At step 1608, the depth images are used toupdate an application. For example, depth images can be used to trackedmotion and/or other user behavior, which can be used, e.g., tomanipulate a game character or other aspects of the application inresponse to movement of a user's body and/or objects around the user,rather than (or in addition to) using controllers, remotes, keyboards,mice, or the like. For example, a video game system can update theposition of images displayed in a video game based on the new positionsof the objects or update an avatar based on motion of the user asdetected based on depth images.

As was discussed above with reference to FIG. 9, step 1602 can involveramping up pulse amplitudes of the RF component of a drive signal whentransitioning from a time during which no light source is driven to emitIR light to a time during which a light source is driven by the drivesignal to emit IR light, and ramping down pulse amplitudes of the RFcomponent of the drive signal when transitioning from a time duringwhich the light source is driven by the drive signal to emit IR light toa time during which no light source is driven to emit IR light. Thiswill result in similar ramping up and ramping down of pulse amplitudesof the light pulses emitted by the light source.

As was discussed above with reference to FIG. 10, step 1602 can involveramping up pulse duty cycles of the RF component of a drive signal whentransitioning from a time during which no light source is driven to emitIR light to a time during which a light source is driven by the drivesignal to emit IR light, and ramping down pulse duty cycles of the RFcomponent of the drive signal when transitioning from a time duringwhich the light source is driven by the drive signal to emit IR light toa time during which no light source is driven to emit IR light. Thiswill result in similar ramping up and ramping down of pulse duty cyclesof the light pulses emitted by the light source.

As was discussed above with reference to FIG. 11, step 1602 can involveramping down temporal gaps and/or how often gaps occur between adjacentpulses or pulse trains of the RF component of a drive signal whentransitioning from a time during which no light source is driven to emitIR light to a time during which a light source is driven by the drivesignal to emit IR light, and ramping up temporal gaps and/or how oftengaps occur between adjacent pulses or pulse trains of the RF componentof the drive signal when transitioning from a time during which a lightsource is driven by the drive signal to emit IR light to a time duringwhich no light source is driven to emit IR light. This will result insimilar ramping down and ramping up of temporal gaps and/or how oftengaps occur between light pulses or pulse trains emitted by the lightsource.

As was discussed above with reference to FIG. 12, step 1602 can involveemitting IR light during integration periods of each frame period aswell as during each of the readout periods between pairs of theintegration periods within each frame period. Such an embodiment reduceshow often there are transitions from times during which IR light isemitted to times during which IR light is not emitted, and vice versa,thereby reducing frequency content associated with such transitions. Incertain embodiments, discussed above with reference to FIG. 14, IR lightcan also be emitted during portions of inter-frame periods.

Additional details of various methods of the present technology can beappreciated from the above discussion of FIGS. 9-15.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims. It is intended that the scopeof the technology be defined by the claims appended hereto.

What is claimed is:
 1. For use by a time-of-flight (TOF) system thatemits and detects infrared (IR) light, a method for substantiallyreducing interference that the TOF system may cause to at least oneother system that is configured to wirelessly receive and respond to IRlight signals, the method comprising: emitting IR light having a lowfrequency (LF) power envelope that is shaped to substantially reducefrequency content within at least one frequency range known to be usedby at least one other system configured to wirelessly receive andrespond to IR light signals, wherein at least a portion of IR lightbeing emitted is radio frequency (RF) modulated IR light; and detectingat least a portion of the emitted RF modulated IR light that hasreflected off one or more objects.
 2. The method of claim 1, wherein theemitting IR light comprises: emitting IR light having a LF powerenvelope that is shaped to substantially reduce frequency content withinthe frequency range from 10 kHz to 100 kHz that is known to be used byother systems for transmitting and receiving remote control signals. 3.The method of claim 1, wherein the emitting IR light comprises: emittingIR light having a LF power envelope that is shaped to substantiallyreduce frequency content within at least two frequency ranges below 3MHz that are known to be used by other systems configured to wirelesslyreceive and respond to IR light signals.
 4. The method of claim 1,wherein: the TOF system is configured to obtain a separate depth imagecorresponding to each of a plurality of frame periods, each frame periodis followed by an inter-frame period, each frame period includes atleast two integration periods, and each integration period is followedby a readout period; and the emitting IR light includes emitting IRlight during each of the integration periods; and to reduce how oftenthere are transitions from times during which IR light is being emittedand times during which IR light is not being emitted, and thereby reducefrequency content associated with the transitions, the emitting IR lightalso includes emitting IR light during the readout periods between pairsof the integration periods within each frame period.
 5. The method ofclaim 1, wherein: the TOF system is configured to obtain a separatedepth image corresponding to each of a plurality of frame periods, eachframe period is followed by an inter-frame period, each frame periodincludes at least two integration periods, and each integration periodis followed by a readout period; and the emitting IR light includesemitting IR light during each of the integration periods; and in orderto decrease a gain level of an automatic gain control (AGC) circuit foruse with an IR light receiver of at least one other system configured towirelessly receive and respond to IR light signals, and thereby make theIR light receiver of the at least one other system less sensitive tointerference from the TOF system, the emitting IR light also includesemitting IR light during at least a portion at least one of: (i) thereadout periods between pairs of the integration periods within eachframe period, or (ii) the inter-frame periods between pairs of frames.6. The method of claim 1, wherein the emitting IR light includes:producing a drive signal including an RF component and having a LF powerenvelope that is shaped to substantially reduce frequency content withinat least one frequency range known to be used by at least one othersystem configured to wirelessly receive and respond to IR light signals;and driving at least one light source with the drive signal includingthe RF component.
 7. The method of claim 6, wherein the producing thedrive signal, including the RF component and having the LF powerenvelope that is shaped to substantially reduce frequency content withinat least one frequency range known to be used by at least one othersystem configured to wirelessly receive and respond to IR light signals,comprises: ramping up pulse amplitudes of the drive signal whentransitioning from a time during which no light source is to be drivento emit IR light to a time during which a said light source is to bedriven by the drive signal to emit IR light; and ramping down pulseamplitudes of the drive signal when transitioning from a time duringwhich a said light source is to be driven by the drive signal to emit IRlight to a time during which no light source is driven to emit IR light.8. The method of claim 7, wherein: the ramping up the pulse amplitudesof the drive signal occurs over a time period of at least 50 μsec; andthe ramping down the pulse amplitudes of the drive signal occurs over atime period of at least 50 μsec.
 9. The method of claim 6, wherein theproducing the drive signal, including the RF component and having the LFpower envelope that is shaped to substantially reduce frequency contentwithin at least one frequency range known to be used by at least oneother system configured to wirelessly receive and respond to IR lightsignals, comprises: ramping up pulse duty cycles of the drive signalwhen transitioning from a time during which no light source is driven toemit IR light to a time during which a said light source is to be drivenby the drive signal to emit IR light; and ramping down pulse duty cyclesof the drive signal when transitioning from a time during which a saidlight source is to be driven by the drive signal to emit IR light to atime during which no light source is driven to emit IR light.
 10. Themethod of claim 6, wherein the producing the drive signal, including theRF component and having the LF power envelope that is shaped tosubstantially reduce frequency content within at least one frequencyrange known to be used by at least one other system configured towirelessly receive and respond to IR light signals, comprises: rampingdown temporal gaps between pulses or pulse trains of the drive signalwhen transitioning from a time during which no light source is driven toemit IR light to a time during which a said light source is driven bythe drive signal to emit IR light; and ramping up temporal gaps betweenpulses or pulse trains of the drive signal when transitioning from atime during which a said light source is driven by the drive signal toemit IR light to a time during which no light source is driven to emitIR light.
 11. The method of claim 6, wherein the producing the drivesignal, including the RF component and having the LF power envelope thatis shaped to substantially reduce frequency content within at least onefrequency range known to be used by at least one other system configuredto wirelessly receive and respond to IR light signals, comprises:ramping down how often gaps occur between pulses or pulse trains of thedrive signal when transitioning from a time during which no light sourceis driven to emit IR light to a time during which a said light source isdriven by the drive signal to emit IR light; and ramping up how oftengaps occur between pulses or pulse trains of the drive signal whentransitioning from a time during which a said light source is driven bythe drive signal to emit IR light to a time during which no light sourceis drive to emit IR light.
 12. The method of claim 1, furthercomprising: producing depth images in dependence on results of thedetecting the at least a portion of the emitted RF modulated IR lightthat has reflected off one or more objects; and updating an applicationin dependence on the depth images.
 13. A time-of-flight (TOF) system,comprising: at least one light source configured to emit infrared (IR)light in response to be driven; a driver configured to drive the atleast one light source to emit IR light having a low frequency (LF)power envelope that is shaped to substantially reduce frequency contentwithin at least one frequency range known to be used by at least oneother system configured to wirelessly receive and respond to IR lightsignals, wherein at least a portion of IR light being emitted is radiofrequency (RF) modulated IR light; and an image pixel detector arrayconfigured to detect at least a portion of the emitted RF modulated IRlight that has reflected off one or more objects and is incident on animage pixel detector array.
 14. The system of claim 13, wherein: the TOFsystem is configured to obtain a separate depth image corresponding toeach of a plurality of frame periods, each frame period is followed byan inter-frame period, each frame period includes at least twointegration periods, and each integration period is followed by areadout period; and the driver is configured to drive a said lightsource to emit IR light during each of the integration periods; thedriver is configured to drive a said light source to emit IR lightduring the readout periods between pairs of the integration periodswithin each frame period, in order to reduce how often there aretransitions from times during which IR light is being emitted and timesduring which IR light is not being emitted, and thereby reduce frequencycontent associated with the transitions; and the light source driven toemit IR light during the readout periods can be the same or differentthan the light source driven to emit IR light during the integrationperiods.
 15. The method of claim 13, wherein: the TOF system isconfigured to obtain a separate depth image corresponding to each of aplurality of frame periods, each frame period is followed by aninter-frame period, each frame period includes at least two integrationperiods, and each integration period is followed by a readout period;and the driver is configured to drive a said light source to emit IRlight during each of the integration periods; the driver is configuredto drive a said light source to emit IR light during at least a portionat least one of (i) the readout periods between pairs of the integrationperiods within each frame period or (ii) the inter-frame periods betweenpairs of frames, in order to decrease a gain level of an automatic gaincontrol (AGC) circuit for use with an IR light receiver of at least oneother system configured to wirelessly receive and respond to IR lightsignals, and thereby make the IR light receiver of the at least oneother system less sensitive to interference from the TOF system; and thelight source that is driven to emit IR light during at least a portionat least one of (i) the readout periods between pairs of the integrationperiods within each frame period or (ii) the inter-frame periods betweenpairs of frames, can be the same as or different than the light sourcedriven to emit IR light during the integration periods.
 16. The systemof claim 13, further comprising: a clock signal generator configured toproduce a clock signal that is provided to the driver; and a processorconfigured to control at least one of the clock signal generator or thedriver.
 17. The system of claim 16, wherein at least one of theprocessor, the clock signal generator or the driver is/are configuredto: ramp up pulse amplitudes of the drive signal when transitioning froma time during which no light source is driven to emit IR light to a timeduring which a said light source is driven by the drive signal to emitIR light; and ramp down pulse amplitudes of the drive signal whentransitioning from a time during which a said light source is driven bythe drive signal to emit IR light to a time during which no light sourceis driven to emit IR light.
 18. The system of claim 16, wherein at leastone of the processor, the clock signal generator or the driver is/areconfigured to: ramp up pulse duty cycles of the drive signal whentransitioning from a time during which no light source is driven to emitIR light to a time during which a said light source is driven by thedrive signal to emit IR light; and ramp down pulse duty cycles of thedrive signal when transitioning from a time during which a said lightsource is driven by the drive signal to emit IR light to a time duringwhich no light source is driven to emit IR light.
 19. The system ofclaim 16, wherein at least one of the processor, the clock signalgenerator or the driver is/are configured to: ramp down temporal gapsbetween, or how often gaps occur between, pulses or pulse trains of thedrive signal when transitioning from a time during which no light sourceis driven to emit IR light to a time during which a said light source isdriven by the drive signal to emit IR light; and ramp up temporal gapsbetween, or how often gaps occur between, pulses or pulse trains of thedrive signal when transitioning from a time during which a said lightsource is driven by the drive signal to emit IR light to a time duringwhich no light source is driven to emit IR light.
 20. One or moreprocessor readable storage devices having instructions encoded thereonwhich when executed cause one or more processors to perform a method forsubstantially reducing interference that a time-of flight (TOF) systemmay cause to at least one other system that is configured to wirelesslyreceive and respond to infrared (IR) light signals, the methodcomprising: producing a drive signal that drives at least one lightsource of the TOF system to emit IR light having a low frequency (LF)power envelope that is shaped to substantially reduce frequency contentwithin at least one frequency range known to be used by at least oneother system configured to wirelessly receive and respond to IR lightsignals; producing depth images in dependence on portions of emitted IRlight that have reflected off one or more objects and are detected by animage pixel detector array of the TOF system; and updating anapplication in dependence on the depth images.